# The Law of Cosines: What is this about?

A Mathematical Droodle

What if applet does not run? |

The applet could serve to demonstrate the Law of Cosines and also the fact that the centers of the squares constructed (externally) on the sides of a parallelogram form a square, which is known as one of V. Thebault's theorems.

### References

- R. Nelsen,
*Proofs Without Words*, MAA, 1993, p. 19

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